This invention relates to apparatus for placing in position on printed circuit boards electronic elements that are taken out of a series of equally spaced packing recesses provided along the length of a tape.
Chip Electronic elements widely used for surface packaging are supplied to users with a reeled base tape having recesses of conforming size to contain individual elements that are provided at equal intervals along the length of the base tape and covered with a detachable cover tape.
A packaging apparatus that uses such component chips supplied in the packing recesses on a tape have an air-cylinder-driven sprocket whose teeth engage with the perforations of the base tape to feed forward the tape and a take-up reel that is intermittently driven by an air cylinder to remove the cover tape away from the base tape so that one chip after another is exposed in the desired position.
A nozzle connected to a vacuum source sucks the exposed chip in position to take it out of the packing recess, with the nozzle and the chip thus removed being then jointly carried to the desired position on a printed circuit board.
Component chips of this type have leads at given points of their packages to establish connection with external circuits. To establish an electric connection with the printed pattern on a circuit board, therefore, each chip must be oriented in conformance therewith. To meet this requirement, the chucks according to U.S. Pat. No. 4,135,630 and Japanese Provisional Utility Model Publication No. 78288 of 1987 have a chip position corrector at the tip of a nozzle that adjusts the direction and position of a chip sucked thereby over a given angle with respect to the reference position of the nozzle.
FIG. 15 shows an example of the chucks just mentioned which comprises a vertically movable suction nozzle 300 positioned at the center and surrounded by four adjustable jaws 306 which are rotatably mounted on pivots 302 and turned by an external drive unit 304.
When brought in contact with a chip surrounded by the tips of the expanded jaws 306 (as indicated by the double-dot-dash line in the figure), the suction nozzle 300 draws the chip to the tip thereof. Then the tips of the jaws 306 come in contact with the chip drawn to the suction nozzle 300 when they are turned thereto by means of the drive unit 304, whereupon the orientation of the chip is changed in conformance with the position and direction of the jaws 306. The adjustment of the chip posture according to the position and direction determined by the jaws 306 permits positioning each chip in exact agreement with the circuit pattern printed on the board.
Now that the jaws 306 turn about the pivots 302 when grasping a chip, the suction nozzle 300 inevitably moves axially. Besides, the long distance between the tips of the jaws and the pivots on which they turn causes a considerable play at the grasping tips of the jaws. Such axial movement and play make the holding of component chips of ultra-small sizes of the order of one millimeter square and the correction of their position and direction extremely difficult.